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Appendix A
How the Service Screw Lifts the Check Valve
When you turn the service screw clockwise 7.5 turns to push open the relief valve stem, a slightly compressible
snap ring in the service screw squeezes past a rim on the inside of the top edge of the check valve as shown in
Figure A-5. As the service screw is turned counterclockwise, the snap ring rises beneath the rim lifting the check
valve. The check valve continues to rise as the service screw is turned ccw until the outer edge of the check valve
contacts the bottom surface of the check valve housing (when you are unscrewing the service screw you will feel
this 'stop'. Continuing to turn the service screw until it is all the way up, compresses the snap ring until it is past
the rim to a degree that the spring in the check valve (and gravity) forces the check down onto its seat in the
manifold. All the way up is the normal operating position of the service screw.
Always make sure to reinstall the plastic protective cap and fully thread it into place to ensure a good seal.
Upper most
position
Chk. vlv.
contact
As the service screw reaches its
its upper-most position, the check
valve's spring (and gravity)
force the check valve down
past the snap ring until it
drops onto its seating
surface in the manifold
(normal operating position)
Check valve contacts
check valve housing
Check valve seating
surface in manifold
Figure A-5. Returning the check valve to its normal operating position
When the check valve contacts
the housing, the snap ring
still supports check valve
Continuing to raise the service
screw to its upper-most limit,
forces the rim inside the
non-moving check valve to
compress the snap ring
Check Valve Operation
service screw
top position
rjpumps\ckvlv6
A-3
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